U.S. patent application number 11/646493 was filed with the patent office on 2007-07-05 for organic thin film transistor and organic light emitting display device including the same.
Invention is credited to Taek Ahn, Tae-Min Kang, Min-Chul Suh.
Application Number | 20070152223 11/646493 |
Document ID | / |
Family ID | 37891456 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070152223 |
Kind Code |
A1 |
Kang; Tae-Min ; et
al. |
July 5, 2007 |
Organic thin film transistor and organic light emitting display
device including the same
Abstract
An organic thin film transistor (OTFT) having a patterned
organic semiconductor layer on top of an electrode wiring layer. In
order to avoid damage to the underlying electrode wiring layer, the
organic semiconductor layer is patterned so that none of the
organic semiconductor layer is removed off the electrode wiring
layer. The patterned organic semiconductor layer completely covers
all of the underlying electrode wiring layer. The OTFT includes a
gate electrode, source and drain electrodes insulated from the gate
electrode and an organic semiconductor layer which is insulated
from the gate electrode and is in contact with the source and drain
electrodes, wherein the organic semiconductor layer completely
covers the source and drain electrodes. In addition, an organic
light emitting display device includes more than one OTFT as well
as an organic light-emitting element electrically connected to the
electrical conductor.
Inventors: |
Kang; Tae-Min; (Suwon-si,
KR) ; Ahn; Taek; (Suwon-si, KR) ; Suh;
Min-Chul; (Suwon-si, KR) |
Correspondence
Address: |
Robert E. Bushnell;Suite 300
1522 K Street, N.W.
Washington
DC
20005-1202
US
|
Family ID: |
37891456 |
Appl. No.: |
11/646493 |
Filed: |
December 28, 2006 |
Current U.S.
Class: |
257/72 ;
257/E51.006; 438/149 |
Current CPC
Class: |
H01L 27/3274 20130101;
H01L 51/052 20130101; H01L 51/0541 20130101; H01L 51/0558 20130101;
H01L 51/0545 20130101 |
Class at
Publication: |
257/072 ;
438/149; 257/E51.006 |
International
Class: |
H01L 29/04 20060101
H01L029/04; H01L 21/84 20060101 H01L021/84 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 2, 2006 |
KR |
10-2006-0000156 |
Claims
1. An organic thin film transistor (OTFT), comprising: a gate
electrode; a source electrode and a drain electrode insulated from
the gate electrode; and an organic semiconductor layer insulated
from the gate electrode and in contact with the source and drain
electrodes, wherein the organic semiconductor layer covers each of
the source and drain electrodes.
2. The organic thin film transistor of claim 1, wherein the source
and drain electrodes are insulated from the gate electrode by a
gate insulating layer.
3. The organic thin film transistor of claim 1, wherein the organic
semiconductor layer comprises a material selected from the group
consisting of pentacene, tetracene, anthracene, naphthalene,
.alpha.-6-thiophen, perylene and a derivative thereof, rubrene and
a derivative thereof, coronene and a derivative thereof, perylene
tetracarboxylic diimide and a derivative thereof, perylene
tetracarboxylic dianhydride and a derivative thereof, polythiophene
and a derivative thereof, polyparaphenylene vinylene and a
derivative thereof, polyfluorene and a derivative thereof,
polythiophene vynylene and a derivative thereof, polyparaphenylene
and a derivative thereof, a polythiophene-heterocyclic aromatic
copolymer and a derivative thereof, oligoacence of naphthalene and
a derivative thereof, oligothiophene of .alpha.-5-thiophene and a
derivative thereof, a metal-containing or metal-free phthalocyanine
and a derivative thereof, pyromellitic dianhydride and a derivative
thereof, pyromellitic diimide and a derivative thereof, perylene
tetracarboxylic acid dianhydride and a derivative thereof,
naphthalene tetracarboxylic acid diimide and a derivative thereof,
naphthalene tetracarboxylic acid dianhydride and a derivative
thereof.
4. The organic thin film transistor of claim 1, wherein the organic
semiconductor layer completely covers each of the source electrode
and the drain electrode.
5. An organic light emitting display device, comprising: a
substrate; an electrical conductor arranged on the substrate; an
organic semiconductor layer covering the electrical conductor; and
an organic light-emitting element electrically connected to the
electrical conductor.
6. The organic light emitting display device of claim 5, further
comprising a pixel circuit electrically connected to the organic
light-emitting element, wherein the electrical conductor is at
least one electrode wiring of the pixel circuit.
7. The organic light emitting display device of claim 6, wherein
the pixel circuit comprises an organic thin film transistor (TFT),
a capacitor, a data wiring layer, a scan wiring layer and a driving
wiring layer.
8. The organic light emitting display device of claim 7, wherein
the organic thin film transistor comprises a gate electrode, and
source and drain electrodes insulated from the gate electrode.
9. The organic light emitting display device of claim 5, wherein
the organic semiconductor layer comprises a material selected from
the group consisting of pentacene, tetracene, anthracene,
naphthalene, .alpha.-6-thiophen, perylene and a derivative thereof,
rubrene and a derivative thereof, coronene and a derivative
thereof, perylene tetracarboxylic diimide and a derivative thereof,
perylene tetracarboxylic dianhydride and a derivative thereof,
polythiophene and a derivative thereof, polyparaphenylene vinylene
and a derivative thereof, polyfluorene and a derivative thereof,
polythiophene vynylene and a derivative thereof, polyparaphenylene
and a derivative thereof, a polythiophene-heterocyclic aromatic
copolymer and a derivative thereof, oligoacence of naphthalene and
a derivative thereof, oligothiophene of .alpha.-5-thiophene and a
derivative thereof, a metal-containing or metal-free phthalocyanine
and a derivative thereof, pyromellitic dianhydride and a derivative
thereof, pyromellitic diimide and a derivative thereof, perylene
tetracarboxylic acid dianhydride and a derivative thereof,
naphthalene tetracarboxylic acid diimide and a derivative thereof,
naphthalene tetracarboxylic acid dianhydride and a derivative
thereof.
10. The organic light emitting display device of claim 5, wherein
the organic semiconductor layer completely covers the electrical
conductor.
11. The organic thin film transistor of claim 1, further comprising
a wiring layer connected to the source and drain electrodes.
12. The organic thin film transistor of claim 11, wherein the
organic semiconductor layer completely covers the wiring layer.
Description
CLAIM OF PRIORITY
[0001] This application makes reference to, incorporates the same
herein, and claims all benefits accruing under 35 U.S.C. .sctn. 119
from an application earlier filed in the Korean Intellectual
Property Office on Jan. 2, 2006 and there duly assigned Ser. No.
10-2006-0000156.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an organic thin film
transistor (OTFT) having a patterned organic semiconductor layer
designed to prevent damage to an underlying electrode wiring layer
formed, and an organic light emitting display device including the
OTFT.
[0004] 2. Description of the Related Art
[0005] Active matrix (AM) organic light emitting display devices
include a pixel circuit for each pixel. A pixel circuit is
electrically connected to a scan line, a data line, and a power
supply line and includes a thin film transistor (TFT) and a storage
capacitor. Organic thin film transistors (OTFTs) use an organic
layer as a semiconductor layer instead of using a silicon layer.
OTFTs can operate at a low temperature and can be used as driving
devices, and thus have been actively researched as possible
switching elements of flexible organic light emitting display
devices.
[0006] An organic light emitting display device that uses OTFTs as
switching devices includes an organic semiconductor layer and a
plurality of electrode wiring layers. When patterning the organic
semiconductor layer, sometimes the underlying electrode wiring
layers can be damaged. In particular, when patterning, sometimes
source and drain electrodes of OTFTs can be damaged.
[0007] OTFTs include an organic semiconductor layer formed on the
source and drain electrodes. In OTFTs, the organic semiconductor
layer covers a portion of the source and drain electrodes because
the organic semiconductor layer is patterned to form only a channel
and not to completely cover the source and drain electrodes.
Accordingly, when patterning an organic semiconductor layer of an
OTFT , the organic semiconductor layer is blanket formed, and then
parts of the organic semiconductor layer that will not become part
of the channel are removed using a laser, etc. Since the source and
drain electrodes and other electrode wiring layers can be damaged
during this removal of the organic semiconductor layer, the OTFT
can be defective. Wherefore, what is needed is a design for a
design for an OTFT and a design for a display using the same that
does not result in a damaged electrode layer.
SUMMARY OF THE INVENTION
[0008] It is therefore an object of the present invention to
provide a design for an OTFT and a design for a display using the
same that does not result in damaged electrode wiring layers.
[0009] It is also an object of the present invention to provide a
design for an OTFT and a design for a display using the same that
allows for a patterned of an organic semiconductor layer without a
damaged underlying electrode wiring layer.
[0010] It is further an object of the present invention to provide
an organic thin film transistor (OTFT) having a patterned organic
semiconductor layer for protecting an electrode wiring layer formed
before the organic semiconductor layer is patterned, and an organic
light emitting display device including the OTFT.
[0011] According to an aspect of the present invention, there is
provided an organic thin film transistor including a gate
electrode, a source electrode and a drain electrode insulated from
the gate electrode and an organic semiconductor layer insulated
from the gate electrode and in contact with the source and drain
electrodes, wherein the organic semiconductor layer covers each of
the source and drain electrodes.
[0012] The source and drain electrodes can be insulated from the
gate electrode by a gate insulating layer. The organic
semiconductor layer can completely cover each of the source
electrode and the drain electrode. The organic thin film transistor
can also include a wiring layer connected to the source and drain
electrodes. This wiring layer can also be completely covered by the
organic semiconductor layer. The organic semiconductor layer can
include a material selected from the group consisting of pentacene,
tetracene, anthracene, naphthalene, .alpha.-6-thiophen, perylene
and a derivative thereof, rubrene and a derivative thereof,
coronene and a derivative thereof, perylene tetracarboxylic diimide
and a derivative thereof, perylene tetracarboxylic dianhydride and
a derivative thereof, polythiophene and a derivative thereof,
polyparaphenylene vinylene and a derivative thereof, polyfluorene
and a derivative thereof, polythiophene vynylene and a derivative
thereof, polyparaphenylene and a derivative thereof, a
polythiophene-heterocyclic aromatic copolymer and a derivative
thereof, oligoacence of naphthalene and a derivative thereof,
oligothiophene of .alpha.-5-thiophene and a derivative thereof, a
metal-containing or metal-free phthalocyanine and a derivative
thereof, pyromellitic dianhydride and a derivative thereof,
pyromellitic diimide and a derivative thereof, perylene
tetracarboxylic acid dianhydride and a derivative thereof,
naphthalene tetracarboxylic acid diimide and a derivative thereof,
naphthalene tetracarboxylic acid dianhydride and a derivative
thereof.
[0013] According to another aspect of the present invention, there
is provided an organic light emitting display device that includes
a substrate, an electrical conductor arranged on the substrate, an
organic semiconductor layer covering the electrical conductor and
an organic light-emitting element electrically connected to the
electrical conductor.
[0014] The organic light emitting display device can also include a
pixel circuit electrically connected to the organic light-emitting
element, wherein the electrical conductor is at least one electrode
wiring of the pixel circuit. The pixel circuit can include an
organic thin film transistor (TFT), a capacitor, a data wiring
layer, a scan wiring layer and a driving wiring layer. The organic
thin film transistor can include a gate electrode, and source and
drain electrodes insulated from the gate electrode. The organic
semiconductor layer can completely cover the electrical
conductor.
[0015] The organic semiconductor layer can include one selected
from the group consisting of pentacene, tetracene, anthracene,
naphthalene, .alpha.-6-thiophen, perylene and a derivative thereof,
rubrene and a derivative thereof, coronene and a derivative
thereof, perylene tetracarboxylic diimide and a derivative thereof,
perylene tetracarboxylic dianhydride and a derivative thereof,
polythiophene and a derivative thereof, polyparaphenylene vinylene
and a derivative thereof, polyfluorene and a derivative thereof,
polythiophene vynylene and a derivative thereof, polyparaphenylene
and a derivative thereof, a polythiophene-heterocyclic aromatic
copolymer and a derivative thereof, oligoacence of naphthalene and
a derivative thereof, oligothiophene of a-5-thiophene and a
derivative thereof, a metal-containing or metal-free phthalocyanine
and a derivative thereof, pyromellitic dianhydride and a derivative
thereof, pyromellitic diimide and a derivative thereof, perylene
tetracarboxylic acid dianhydride and a derivative thereof,
naphthalene tetracarboxylic acid diimide and a derivative thereof,
naphthalene tetracarboxylic acid dianhydride and a derivative
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] A more complete appreciation of the invention, and many of
the attendant advantages thereof, will be readily apparent as the
same becomes better understood by reference to the following
detailed description when considered in conjunction with the
accompanying drawings in which like reference symbols indicate same
or similar components, wherein:
[0017] FIG. 1 is a view of a circuit diagram of a pixel circuit
(PC) used in an organic light emitting display device according to
an embodiment of the present invention;
[0018] FIG. 2 is a detailed view of a circuit diagram of the PC of
FIG. 1;
[0019] FIG. 3 is a view of electrode wiring layers of a bottom gate
type organic light emitting display device according to an
embodiment of the present invention;
[0020] FIG. 4 is a view of a patterned organic semiconductor layer
formed on the electrode wiring layers of the bottom gate type
organic light emitting display device of FIG. 3;
[0021] FIG. 5 is a cross-sectional view of the bottom gate type
organic light emitting display device taken along line V-V of FIG.
3;
[0022] FIG. 6 is a cross-sectional view of the bottom gate type
organic light emitting display device taken along line VI-VI of
FIG. 3; and
[0023] FIG. 7 is a schematic cross-sectional view of a top gate
type organic light emitting display device according to another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Turning now to the figures, FIG. 1 is a view of a circuit
diagram of a pixel circuit (PC) used in an organic light emitting
display device according to embodiment of the present invention. As
illustrated in FIG. 1, each of a plurality of pixels in the organic
light emitting display device includes a data line DATA, a scan
line SCAN and an organic light-emitting element and a power supply
line Vdd that supplies power to the OLED. The PC of each pixel is
electrically connected to the data line DATA, the scan line SCAN
and the power supply line Vdd and controls the light emission of
the OLED.
[0025] Turning now to FIG. 2, FIG. 2 is a detailed view of a
detailed circuit diagram of the PC of FIG. 1 according to an
embodiment of the present invention. The PC includes a driving TFT
M1, a switching TFT M2, and a single storage capacitor Cst.
Referring to FIG. 2, each pixel of the organic light-emitting
display device according to the present embodiment of the present
invention includes at least two thin film transistors, namely, the
switching TFT M2 and the driving TFT M1, the storage capacitor Cst,
and the OLED.
[0026] The switching TFT M2 is turned on/off by a scan signal
received by the scan line SCAN and delivers a data signal from the
data line DATA to the storage capacitor Cst and the driving TFT M1.
The present invention is not limited to the case in which the
switching TFT M2 is a single TFT as illustrated in FIG. 2.
Alternatively, a switching device can include a plurality of TFTs
and a capacitor. The pixel of FIG. 2 can further include a circuit
which compensates for the Vth value of the driving TFT M1 or a
circuit which compensates for the voltage drop in the power supply
line Vdd.
[0027] The driving TFT M1 determines the amount of current flowing
into the OLED according to the data signal received through the
switching TFT M2. The storage capacitor Cst stores the data signal
received through the switching TFT M2 for one frame.
[0028] Although the driving TFT M1 and the switching TFT M2 are
illustrated as PMOS TFTs in FIG. 2, the present invention is not
limited thereto. At least one of the driving TFT M1 and the
switching TFT M2 can be implemented as an NMOS TFT. In addition,
the number of TFTs and the number of capacitors are not limited to
those illustrated in FIG. 2. In other words, a greater number of
TFTs and a greater number of capacitors than those illustrated in
FIG. 2 can be included.
[0029] Turning now to FIGS. 3 through 6, FIG. 3 is a view of
electrode wiring layers of a bottom gate type organic light
emitting display device 100 according to an embodiment of the
present invention, FIG. 4 is a view of a patterned organic
semiconductor layer formed on the electrode wiring layers of the
bottom gate type organic light emitting display device 100 of FIG.
3, FIG. 5 is a cross-sectional view of the bottom gate type organic
light emitting display device 100 taken along a line V-V of FIG. 3,
and FIG. 6 is a cross-sectional view of the bottom gate type
organic light emitting display device 100 taken along a line VI-VI
of FIG. 3
[0030] Referring now to FIG. 3, driving TFT M1 includes a first
source electrode 111, a first drain electrode 112 and a first gate
electrode 113. Switching TFT M2 includes a second source electrode
121, a second drain electrode 122 and a second gate electrode 123.
A data wiring layer 130 constituting a data line DATA is
electrically connected to the second source electrode 121. A scan
wiring layer 140 constituting the scan line SCAN is electrically
connected to the second gate electrode 123. A driving wiring layer
150 constituting the power supply line Vdd is electrically
connected to the first source electrode 111. A pixel electrode 160
is electrically connected to the first drain electrode 112. In
addition, a first capacitor layer 171 included in a storage
capacitor Cst is connected to the second drain electrode 122
through a contact hole (not shown). A second capacitor layer 172 is
arranged so as to be electrically connected to the driving wiring
layer 150.
[0031] Here, the first source electrode 111, the first drain
electrode 112, the second source electrode 121, the second drain
electrode 122, the data wiring layer 130, the driving electrode
150, and the second capacitor layer 172 are formed on a gate
insulating layer 193. The first gate electrode 113, the second gate
electrode 123, the scan wiring layer 140, and the first capacitor
layer 171 are formed on a buffer layer 192. The first source
electrode 111, the first drain electrode 112, the second source
electrode 121, the second drain electrode 122, the data wiring
layer 130, the driving electrode 150, the second capacitor layer
172, the first gate electrode 113, the second gate electrode 123,
the scan wiring layer 140, and the first capacitor layer 171 are
all electrical conductors.
[0032] After each of the electrodes are formed, an organic
semiconductor layer is formed on a gate insulating layer 193. After
forming the organic semiconductor layer, the organic semiconductor
layer is patterned using a laser ablation (LAT) method.
[0033] When the organic semiconductor layer is patterned, parts of
the organic semiconductor layer to be removed are denoted by the
shaded area (P) of FIG. 4. By doing so, no metal is exposed so that
there is no removal of any of the organic semiconductor layer that
covers the electrode wiring layer. Specifically, each of the first
source electrode 111, the first drain electrode 112, the second
source electrode 121, the second drain electrode 122, the data
wiring layer 130, the driving wiring layer 150, and the second
capacitor layer 172 formed on the gate insulating layer 193 are
still totally covered with the organic semiconductor layer, even
after the patterning of the organic semiconductor layer.
[0034] It is to be appreciated that the LAT process in the
patterning of the organic semiconductor layer can damage an
underlying electrode wiring layer, especially when the organic
semiconductor layer is removed off an underlying electrode wiring
layer. Therefore, the present invention avoids this damage to the
electrode wiring layer by only removing portions of the organic
semiconductor layer that do not lye on top of the electrode wiring
layer.
[0035] Turning now to FIGS. 5 and 6, FIGS. 5 and 6 each illustrate
cross-sectional views of the bottom gate type organic light
emitting display device 100 including an organic semiconductor
layer 180 after the patterning as described above, according to an
embodiment of the present invention. Referring to FIG. 5, the
buffer layer 192 is formed on a substrate 191. The first gate
electrode 113 is formed on the buffer layer 192. After forming the
first gate electrode 113, the gate insulating layer 193 is formed
so as to cover the first gate electrode 113.
[0036] Here, the substrate 191 can be a glass substrate, a plastic
substrate or a metal substrate. The metal substrate can be formed
of metal foil, for example, stainless steel, Ti, Mo, an Invar
alloy, an Inconel alloy, a Kovar alloy, or the like. The plastic
substrate can include a plastic film made out of either
polyethersulphone (PES), polyacrylate (PAR), polyetherimide (PEI),
polyethyelenen napthalate (PEN), polyethyeleneterepthalate (PET),
polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate
(PC), cellulous triacetate (TAC) or cellulose acetate propinonate
(CAP).
[0037] The buffer layer 192 is formed of an organic compound and/or
an inorganic compound, preferably, SiO.sub.x (x.gtoreq.1) or
SiN.sub.x (x.gtoreq.1). The gate insulating layer 193 can be an
organic insulating layer, an inorganic insulating layer or an
organic-inorganic hybrid layer, and can be formed as a
single-layered or multi-layered structure.
[0038] Meanwhile, after forming the gate insulating layer 193, the
first source electrode 111 and the first drain electrode 112 are
formed on the gate insulating layer 193. The organic semiconductor
layer 180 is formed using the patterning as described above. Here,
the organic semiconductor layer 180 covers the first source
electrode 111 and the first drain electrode 112 completely.
[0039] The first source electrode 111, the first drain electrode
112 and the first gate electrode 113 are formed of materials having
good electrical conductivity, such as a metal such as Ag, Mg, Al,
Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, a compound thereof, or the
like.
[0040] The organic semiconductor layer 180 can be formed of at
least one of pentacene, tetracene, anthracene, naphthalene,
.alpha.-6-thiophen, perylene and a derivative thereof, rubrene and
a derivative thereof, coronene and a derivative thereof, perylene
tetracarboxylic diimide and a derivative thereof, perylene
tetracarboxylic dianhydride and a derivative thereof, polythiophene
and a derivative thereof, polyparaphenylene vinylene and a
derivative thereof, polyfluorene and a derivative thereof,
polythiophene vynylene and a derivative thereof, polyparaphenylene
and a derivative thereof, a polythiophene-heterocyclic aromatic
copolymer and a derivative thereof, olignaphthalene and a
derivative thereof, oligothiophene of .alpha.-5-thiophene and a
derivative thereof, a metal-containing or metal-free phthalocyanine
and a derivative thereof, pyromellitic dianhydride and a derivative
thereof, pyromellitic diimide and a derivative thereof, perylene
tetracarboxylic acid dianhydride and a derivative thereof,
naphthalene tetracarboxylic acid diimide and a derivative thereof,
naphthalene perylene tetracarboxylic acid dianhydride and a
derivative thereof
[0041] Referring now to FIG. 6, the second capacitor layer 172 is
formed on the gate insulating layer 193, wherein the organic
semiconductor layer 180 is formed using the patterning as described
above to cover the second capacitor layer 172 completely. A
planarized insulating layer 194 is further formed to cover the
organic semiconductor layer 180. The pixel electrode 160 is formed
on the planarized insulating layer 194 while electrically
connecting to the first drain electrode 112 through a contact hole
194a. The contact hole 194a can be formed using a laser etching
method, a photolithographic method, or the like.
[0042] After forming the pixel electrode 160, a pixel definition
layer 195 is formed so as to cover the pixel electrode 160. A
predetermined opening 195a is formed in the pixel definition layer
195. The pixel definition layer 195 can be an organic insulating
layer, an inorganic insulating layer or an organic-inorganic hybrid
layer, and can be formed as a single-layered or a multi-layered
structure.
[0043] The organic insulating layer can be formed of polymer
materials, for example, a general purpose compound (PMMA, PS), a
polymer derivative including a phenol group, a acryl-based polymer,
an imide-based polymer, an aryl ether-based, an amide-based
polymer, a fluorine-based polymer, a p-xilylene-based polymer, a
vinyl alcohol-based polymer, a blend thereof, or the like. The
inorganic insulating layer can be SiO.sub.2, SiNx, SiON,
Al.sub.2O.sub.3, TiO.sub.2, Ta.sub.2O.sub.5, HfO.sub.2, ZrO.sub.2,
BST, PZT, or the like.
[0044] The pixel definition layer 195 can be formed using an ink
jet printing method. First, some parts of the pixel electrode 160
are surface-treated. In cases where the adhesive force between an
untreated substrate surface and the ink is good, a fluorine-based
plasma is used to make portions of the substrate surface that
corresponds to opening 195a water-repellant. Here, fluorine-based
gases such as CF.sub.4 or C.sub.3F.sub.8 are used in the surface
treatment with the fluorine-based plasma. The pixel definition
layer 195 is then formed by discharging a solution including
insulating materials for the pixel definition layer 195 from an
inkjet head. The opening 195a exposing the pixel electrode 160
through the pixel definition layer 195 is formed on the
surface-treated parts of the pixel electrode 160.
[0045] In cases where the adhesive force between the untreated
substrate surface and an ink is poor, that is, the substrate
surface is water-repellant, the pixel definition layer 195 can be
formed by surface-treating portions of the substrate surface that
do not correspond to opening 195a with Ar and O.sub.2 plasmas. That
is, by surface-treating the parts of the substrate surface except
for the pixel electrode 160 corresponding to the opening 195a using
Ar and O.sub.2 plasmas, the substrate surface is hydrophilized to
increase the adhesive force. Next, when ink including insulating
materials for forming the pixel definition layer 195 is discharged
on the substrate surface, the pixel definition layer 195 is coated
on only the surface-treated parts having the increased adhesive
force. Accordingly, the pixel definition layer 195 is not formed on
a surface of the pixel electrode 160 which is not surface-treated
with plasma. Meanwhile, an organic light emitting layer 196 and an
opposite electrode 197 are stacked on the exposed pixel electrode
160 sequentially. Here, the opposite electrode 197 is formed to
cover all the pixels, but the structure of the opposite electrode
197 is not limited thereto. That is, the opposite electrode 197 can
be patterned.
[0046] When the pixel electrode 160 is an anode electrode, the
opposite electrode 197 is a cathode electrode, or vice versa. In
the current embodiment of the present invention, the pixel
electrode 160 is an anode electrode.
[0047] When the organic light emitting display device 100 is a
bottom emission type organic light emitting display device, the
pixel electrode 160 can be a transparent electrode, and the
opposite electrode 197 can be a reflective electrode. Here, the
transparent electrode has a high work function, and can be formed
of transparent ITO, IZO, In.sub.2O.sub.3, ZnO, or the like. The
reflective electrode constituting the opposite electrode 197 is
formed of a metal such as Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr,
Li, Ca or a compound thereof having a low work function.
[0048] When the organic light emitting display device 100 is a top
emission type organic light emitting display device, the pixel
electrode 160 can be the reflective electrode, and the opposite
electrode 197 can be the transparent electrode. Here, the
reflective electrode constituting the pixel electrode 160 can be
formed by forming a reflective layer with Ag, Mg, Al, Pt, Pd, Au,
Ni, Nd, Ir, Cr, Li, Ca, a compound thereof, or the like, and
forming ITO, IZO, ZnO, In.sub.2O.sub.3 or the like having a high
work function on the reflective layer. The transparent electrode
constituting the opposite electrode 197 is formed by depositing Ag,
Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, a compound thereof, or
the like having a low work function, and forming thereon a
subsidiary electrode layer or a bus line with transparent materials
such as ITO, IZO, ZnO, In.sub.2O.sub.3, and the like.
[0049] When the organic light emitting display device 100 is a dual
emission type organic light emitting display device, both the pixel
electrode 160 and the opposite electrode 197 can be transparent
electrodes.
[0050] Materials for forming the pixel electrode 160 and opposite
electrode 197 are not limited to the materials described above,
that is, the pixel electrode 160 and opposite electrode 197 can be
formed of electrically conductive materials, conductive pastes
including conductive particles such as Ag, Mg, Cu, etc., or the
like. When the pixel electrode 160 and the opposite electrode 197
are formed of conductive pastes, the conductive pastes can be
printed using an ink jet printing method. After printing, the
conductive pastes are sintered to form the pixel electrode 160 and
the opposite electrode 197.
[0051] The organic light emitting layer 196 can be a small
molecular weight organic layer or a polymer organic layer. When the
organic light emitting layer 196 is a small molecular weight
organic layer, a Hole Injection Layer (HIL), a Hole Transport Layer
(HTL), an Emission Layer (EML), an Electron Transport Layer (ETL),
an Electron Injection Layer (EIL), or the like are stacked to have
a single or multi-layer structure. The organic light emitting layer
196 can be formed of organic materials such as copper
phthalocyanine (CuPc),
N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPB),
tris-8-hydroxyquinoline aluminum (Alq.sub.3), or the like, but
materials for forming the organic light emitting layer 196 are not
limited thereto. The small molecular weight organic layer can be
formed using a vapor deposition method.
[0052] The polymer organic layer can generally include a HTL and an
EML. Here, the HTL can be formed of PEDOT. The EML can be formed of
polymer organic materials such as Poly-Phenylenevinylene
(PPV)-based materials, Polyfluorene-based materials, or the like
using a screen printing method, an ink jet printing method, or the
like.
[0053] After the bottom gate type organic light emitting display
device 100 is formed, an upper part thereof is sealed to provide
protection from the atmospheric.
[0054] According to the current embodiment of the present
invention, by patterning the organic semiconductor layer 180 so as
to completely cover the electrode wiring layers formed on the gate
insulating layer 193, that is the first source electrode 111, the
first drain electrode 112, the second source electrode 121, the
second drain electrode 122, the data wiring layer 130, the driving
wiring layer 150, and the second capacitor layer 172, the electrode
wiring layers are not damaged during the patterning of the organic
semiconductor layer 180.
[0055] Turning now to FIG. 7, FIG. 7 is a schematic cross-sectional
view of an organic light emitting display device 200 according to
another embodiment of the present invention. The organic light
emitting display device 200 is a top gate type organic light
emitting display device. The structure of the top gate type organic
light emitting display device 200 is described as follows with
reference to FIG. 7.
[0056] First, a buffer layer 292 is formed on a substrate 291. A
first source electrode 211 and a first drain electrode 212 are
formed on the buffer layer 292. Although not illustrated in FIG. 7,
a second source electrode, a second drain electrode, a data wiring
layer, a driving wiring layer, and a second capacitor layer can
also be formed on the buffer layer 292.
[0057] After forming an organic semiconductor layer 280 similar to
the organic layer 180 of the bottom gate type organic light
emitting display device 100, the organic semiconductor layer 280 is
patterned using a LAT method. The organic semiconductor layer 280
is patterned so that the patterned organic semiconductor layer
completely covers each of the first source electrode 211 and the
first drain electrode 212. Although not illustrated in FIG. 7, the
organic semiconductor layer 280 is patterned so as to completely
cover other electrode wiring layers formed on the buffer layer 292,
such as a second source electrode, a second drain electrode, a data
wiring layer, a driving wiring layer, and a second capacitor
layer.
[0058] When the top gate type organic light emitting display device
200 is patterned using the LAT method, since some parts of the
organic semiconductor layer 280 and electrodes under the organic
semiconductor layer 280 can be damaged, parts of the organic
semiconductor layer to be removed are parts of the organic
semiconductor layer not covering an electrode wiring layer formed
on the buffer layer 292.
[0059] Next, a gate insulating layer 293 is further formed so as to
cover the organic semiconductor layer 280, and a first gate
electrode 213 and a pixel electrode 260 are formed on the gate
insulating layer 293. Although not illustrated in FIG. 7, a second
gated electrode, a scan wiring layer, and a first capacitor layer
are also formed on the gate insulating layer 293.
[0060] After forming the first gate electrode 213, the pixel
electrode 260, etc. on the gate insulating layer 293, a pixel
definition layer 295, through which an opening 295a is formed, is
formed on the gate insulating layer 293. An additional contact hole
293a is formed in the gate insulating layer 293 and the organic
semiconductor layer 280 to electrically connect the pixel electrode
260 and the first drain electrode 212.
[0061] An organic light emitting layer 296 and an opposite
electrode 297 are stacked on the exposed pixel electrode 260
sequentially. After forming the top gate type organic light
emitting display device 200, an upper part of the organic light
emitting display device 200 is sealed to provide protection from
the atmosphere.
[0062] The structures of the first source electrode 211, the first
drain electrode 212, the first gate electrode 213, the pixel
electrode 260, the organic semiconductor layer 280, the substrate
291, the buffer layer 292, the gate insulating layer 293, the pixel
definition layer 295, the organic light emitting layer 296, and the
opposite electrode 297 illustrated in FIG. 7 are equivalent to the
first source electrode 111, the first drain electrode 112, the
first gate electrode 113, the pixel electrode 160, the organic
semiconductor layer 180, the substrate 191, the buffer layer 192,
the gate insulating layer 193, the pixel definition layer 195, the
organic light emitting layer 1296, and the opposite electrode 197
of the organic light emitting display device 100 respectively, and
thus detailed descriptions thereof has been omitted.
[0063] According to the current embodiment of the present
invention, by patterning the organic semiconductor layer 280 so as
to completely cover all the electrode wiring layers formed on the
buffer layer 292, that is the first source electrode 211, the first
drain electrode 212, the second source electrode, the second drain
electrode, the data wiring layer, the driving wiring layer, and the
second capacitor, the electrode wiring layers are not damaged
during patterning of the organic semiconductor layer 280.
[0064] As the structure, operation, and effect of the organic light
emitting display device 200 other than described herein are the
same as the structure, operation, and effect of the organic light
emitting display device 100 illustrated in FIGS. 1 through 6, a
detailed descriptions thereof has been omitted.
[0065] Although the present invention is applied to an organic
light emitting display device, the present invention can also be
applied to various kinds of flat display devices such as liquid
crystal display devices, etc. in which an organic semiconductor
layer can be used. As described above, by applying a patterned
organic semiconductor layer for protecting electrode wiring layers
formed before the organic semiconductor layer is patterned, the
electrode wiring layers can be protected, and the quality of
product can be improved.
[0066] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details can be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
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